Neutron-Scattering Study of Magnons and Paramagnons in a Chromium-Manganese Alloy

The inelastic magnetic scattering from a single crystal of ${\mathrm{Cr}}_{0.98}$ ${\mathrm{Mn}}_{0.02}$ alloy has been studied both below and above the Néel temperature. Measurements at 300 K using the diffraction method have yielded a value for the spin-wave velocity of 1.29±0.26×${10}^7$ cm/sec in good agreement with theoretical predictions. At a temperature of $1.16T_{\mathrm{N}}$ inelastic magnetic scattering persists strongly even though there is no ordered or localized moment. This scattering has been interpreted as being due to paramagnonlike excitations, and a line-shape calculation based on this theory fits the experimental results quite well.